I had this very issue. Had the phone about a month and not sure if it was an app or a setting, but the battery went wicked hot and the charge just left the building after that. I couldn't figure it out. Did lots of research here on the forums and decided that ATK wasn't the answer (which you've heard now too). I also got a new battery from VZW on warranty and while they suggested using ATK (I think they all do for some reason) I didn't.
Not sure of the thread, cause there are so many that address the battery, but there is some very simple things to consider that have been stated many times. Your settings and what you are asking the phone to do is one primary thing to consider. I suggest starting at the top of the settings tree and look into each one and see how you have it set...display brightness, battery mode, data push, retrieval schedules, background data, notifications...and then look at your home screen(s) and widgets. Widgets take up battery cause they are pulling down as needed. It's probably not one single thing that your phone is doing or has done, but a multitude of little things that are berating your processor to stay active. The more actions, less sleep, the battery and processor get hot, which degrades battery life exponentially quicker.
Just to see, I adjusted everything to manual pushes and retrievals, eliminated most of my widgets, set to battery saver mode, and took the brightness to 30%, etc...AFTER I did a factory reset with the new battery from VZW. Basically, I started from scratch but with a new battery and the least pull on the settings. Slowly from there I added the things I wanted it to do. Not that you should do this, but I would consider it. Definitely update your DX to 2.2 as I am told, one of the issues addressed was the battery. Even before I went to 2.2, I had fixed my battery issues. I'm now rooted and have settings pretty mild. Fetch schedule is on the hour, only the power control widget, wi-fi is on whenever I'm home (over 3g while in the house), auto-sync Facebook over wi-fi only, and no task killer. Depending on how much use I put the phone against in a day truly determines how long of a charge I get. Light use can be up to two days, heavy use...8 hours.
Just some considerations.
I hope that helps in some way.
-Andy
***EDIT*** I run the power control, weather channel, slacker radio, sticky note, and calendar widgets.